Luffing crane



June 30, 1970 H. TAX 3,517,829

LUFFING CRANE Filed Aug. 2, 1967 s Sheets-Sheet 1 Fig.1

lIVl/[iIV/UR Hans Bk 1 June 30, 1910 3,1 3,517,829

' 'LUFFING CRANE Filed Aug. 8, 1967 3 Sheets-Sheet :3

June 30, 1970 H. TAX

wrrme cum:

3 sheets-sheet 3 Filed Aug. 8. 1967 INVENTOR- Hd s Tra I/QMM Bum3,517,829 7 LUFFING CRANE Hans Tax, 3 Potsdamer Strasse, 8 Munich 23,Germany Filed Aug. 8, 1967, Ser. No. 659,102 Claims priority,applicatiglli sggmany, Aug. 12, 1966,

Int. Cl. 1266c 23/10 US. Cl. 212-8 1 Claim ABSTRACT OF THE DISCLOSUREBACKGROUND OF THE INVENTION This invention relates to cranes, andparticularly to luifing cranes of the type commonly used in harbor in-.stallations, and usually mounted on revolving bases.

Such cranes normally have an upright post, a jib pivotally attached tothe bottom end of the post, and a load rope or the like, one end ofwhich is attached to a winch on the crane base. The rope passes over aguide pulley near the top of the post and an idler at the free end ofthe jib. Provisions must be made for moving a load suspended from therope in an approximately horizontal path when the jib is pivoted on thepost.

Approximately horizontal movement is desirable to facilitate visualcontrol of load movement by the crane operator and to minimize the powerrequired for pivotally moving the jib. It is furthermore advantageousthat the path of the load have an initial slightly descending portionand a final slightly ascending portion in order to reduce the energyrequired for starting the horizontal movement of the load and to absorbmost of this energy at the end of the movement.

The simplest known cranes which satisfy the aforeenumerated requirementshave a load rope which is reeved over a three-sheaved block arrangementmounted between the free ends of the post and the jib. The triple ropestrands necessarily sag and oscillate transversely. When the length ofthe jib is of the order of at least meters, as in many harbor cranes,the multiple ropes tend to tangle.

Numerous other devices have been proposed for controlling the movementof a load in the desired manner during angular displacement of the jibon the post. These known devices are either complex and correspondinglycostly to build and maintain, or they can move a load only in a pathwhich significantly deviates from the preferred path outlined above.

The object of the invention is the provision of a level lufiing crimewhich is simple, and hence inexpensive to build and maintain, and whichpermits the desired control of load movement.

SUMMARY OF THE INVENTION In one of its basic aspects, this inventionresides in a crane of the general type described above in which a secondpivot on the jib is offset in a direction toward the United StatesPatent 0 "Ice free jib end from the first-mentioned pivot connecting thejib and post. A third pivot is upwardly offset on the post from thefirst pivot. Two links are respectively attached to the second and thirdpivots and connected by a fourth pivot spaced from the second and thirdpivots so that the two links and the portion of the jib between thefirst and second pivots constitute three members of a four-bar linkagein which the portion of the post between the first and third pivots isthe fourth member.

In addition to the afore-mentioned guide pulley at the top of the post,a second guide pulley is mounted on one of the three linkage membersother than the post, and a third guide pulley on the top part of thepost. A load rope, chain, or cable, hereinafter referred to as the loadrope member, is trained from the first guide pulley in sequence over thesecond and third guide pulleys toward the idler at the free end of thejib.

Other features, additional objects, and many of the attendant advantagesof this invention will readily be appreciated as the same becomes betterunderstood by reference to the following detailed description ofpreferred embodiments when considered in connection with theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 shows a crane of the invention in fragmentary side elevation; and

FIG. 2 illustrates a modification of the crane of FIG. 1 in acorresponding view.

FIG. 3 shows the relative dimensions of a crane according to FIGS. 1 and2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring initially to FIG. 1,there is seen a harbor crane having a base 10 provided with a turntable12 on which an upright post 14 is mounted. The operators cabin and thepower source of the crane form an integral part of the post and have notbeen shown in detail, nor has the winch been shown which is alsoinstalled in the bottom end of the post 14.

A first pivot 16 on the bottom part of the post attaches a jib 18 to thepost. The free end of the jib, not seen in the drawing, is provided withan idler sheave in the usual manner. A link 20 is attached to the jib bya second pivot 22, and a link 24 is similarly attached to the post 14 bya third pivot 26. The links are connected by a fourth pivot 28. The fourpivots have parallel axes and are spaced from each other so that the twolinks 20, 24 and respective portions 30, 32 of the jib and of the postform a plane four-bar linkage in which the jib portion 30 is much longerthan any of the other three bars.

A guide pulley 34 is coaxially mounted on the fourth pivot 28. The loadrope member 36 of the crane extends upward from the winch (not shown) toa guide pulley 38 on the top of the post 14, is then trained over thepulley 34, another guide pulley 40 coaxial with the pulley 38, andultimately over the non-illustrated idler sheave on the jib from whichthe end of the rope member depends.

A screw jack 42 is fixedly mounted on the post 14 and its extensiblemember is attached to the link 24.

The crane illustrated in FIG. 2 is closely similar to that describedabove with reference to FIG. 1. Identical elements have been providedwith the same reference numerals, and do not require separatedescription. The post 14 is modified to provide a slideway 46 for acounterweight 44 suspended from one end of a tension member 48, such asa rope, cable, or chain, which is trained over a pulley 50, coaxial withthe afore-described pulleys 38, 40. The slideway slopes steeply, but isnot vertical. The other end of the tension member 48 is attached by afastener 52 to a link arranged in the manner of the aforedescribed link20. The fastener 52 is equidistant from the pivots 22, 28, and the link20 is wider than the link 20 to withstand the transverse stressestransmitted by the tension member 48.

Both embodiments of the invention operate similarly.

When the jib 18 is close to the horizontal position, and the momentproduced by its weight is near its maximum value, the four-bar linkageacts in the manner of a toggle to apply the tension of the rope member36 to the jib 18 under conditions of maximum torque to balance themoment produced by the weight of the jib. When the jib 18 approaches itsterminal position near the post 14 (14), and the moment produced by itsweight approaches a minimum value, the tension of the rope member isabout equally transmitted to the links 20 (20'), 24 so that the momentapplied to the jib by the rope member reaches its minimum.

The height of the post, the length of the jib, the location of the firstpivot 16, and other dimensional characteristics of a luffing crane andthe speed of its movement are normally determined by the intendedapplication. The theory of four-bar linkages is well developed, and thelocations of the pivots 22, 26, 28 and of the pulley 34 are readilydetermined by routine calculations to produce any desired movement ofthe load attached to the rope member, including a fiat path withterminal portions which slope upward from the substantially horizontalcentral portion of the path. A rise by about 0.7 times the horizontalsweep of the load is normally preferred.

The whipping movement of the crane jib is actuated by the jack 42 whichmay be replaced by any other connecting element whose length can bevaried, such as a hydraulic motor or the like, and which is interposedbetween the post 14 (14') and one of the otherthree members of thefour-bar linkage. It is advantageous hingedly to attach the connectingelement to the link 24 because this arrangement requires only a singlepivot pin to be released if it is desired completely to lower the jib18.

The counterweight arrangement shown in FIG. 2 can readily balance theweight of the jib 18 in a very simple manner in practically any angularposition of the jib. It is as effective as a counterweight mounted on anextension of the jib beyond the pivot 16 without requiring the com plexjib structure necessary when the jib is to extend beyond the post in twodirections. It will be appreciated that the weight of the jib cannot bebalanced uniformly, or even approximately uniformly in all angularpositions of the jib, when a tension member carrying a counterweight isdirectly attached to the jib. The members of the fourbar linkage of thisinvention, and particularly the links 20', 24, move in very differentindividual paths. The point on one of the links to which the tensionmember 48 is to be attached to produce a desired result is readilycalculated in a conventional manner.

The dimensional relationships of the four pivots in the four-bar linkageand the locations of the guide pulleys shown in the drawing arerepresentative of successful practice of this invention in a cranehaving other dimenvention, and that it is intended to cover all changesand modifications of the examples of the invention herein chosen for thepurpose of the disclosure which do not constitute departures from thespirit of the invention.

FIG. 3 shows the relative dimensions of the crane according to the FIG.1 and 2. The different dimensions have in one embodiment of thisinvention the following values:

a=100, 17:25, 0:9.6, 02:5, e=10, f=9,6, h: 10, i=4.3.

With these relative dimensions an approximately horizontal path of thesuspended load is achieved when the jib is pivoted. Further this path ofthe load has a slightly descending portion at the one end and a slightlyascend ing portion at the other end.

What is claimed is:

1. In a level-luffing crane, the combination of an up wardly extendingpost, a first pivot on the bottom portion of said post, a jib having oneend thereof attached to said first pivot and also having a free end, asecond pivot on said jib offset from said first pivot, a third pivot onsaid post upwardly ofiset from said first pivot, two links respectivelyattached to said second and third pivots, a fourth pivot spaced fromsaid second and third pivots and connecting said links together,actuating means for raising and lowering said jib about said firstpivot, the distance between said first and second pivots being asubstantially greater than that between the first and third pivots andalso being substantially greater than the length of each of said links,a pair of guide pulleys mounted coaxially at the top of said post, athird guide pulley mounted on said fourth pivot, and a load rope memberextending from a winch in the bottom portion of said post, said ropemember being reeved consecutively around one of the pair of guidepulleys at the top of said post, around said third guide pulley on saidfourth pivot, and around the other of the pair of guide pulleys at thetop of the post before extending to an idler pulley at the free end ofsaid jib.

References Cited UNITED STATES PATENTS HARVEY C. HORNSBY, PrimaryExaminer U.S. Cl. X.R, 212-48, 59

